A team of astronomers using the James Webb Space Telescope has found tiny dust particles traveling far from their home galaxy, surviving a perilous journey through a harsh cosmic environment that should have destroyed them.
The James Webb Space Telescope (JWST) findings offer new insight into how galaxies “breathe,” grow and recycle the raw materials that fuel future generations of stars.
“Before this study, there had not been a direct detection of dust on such a large scale,” lead author Sylvain Veilleux, an astronomy professor at the University of Maryland, College Park, said in a statement. “Webb was the key that made it happen.”
The dust originates from the distant galaxy Makani (Hawaiian for “wind”; officially SDSS J211824.06+001729.4), a compact but massive galaxy that recently underwent intense bursts of star formation — one 7 million years ago and another 0.4 billion years ago. These stellar fireworks generated extraordinarily powerful galactic winds, first detected in 2019, spanning a whopping 326,200 light-years, propelling gas and dust outward into the galaxy’s vast halo of hot gas, known as the circumgalactic medium, or CGM.
Using the JWST’s infrared instruments, a team led by Veilleux detected the faint glow of polycyclic aromatic hydrocarbons (PAHs), which are complex organic molecules that cling to dust grains and serve as tracers of how dust behaves while traveling through a galaxy’s harsh environment.
The team found that much of the dust remarkably survived long enough to reach the CGM, though it shows signs of erosion. PAH molecules shrink and become more ionized with increasing distance from the galaxy’s core, suggesting gradual destruction over roughly 100 million years, the study reports.
As the dust travels outward, it encounters gases hotter than about 17,000 degrees Fahrenheit (about 10,000 degrees Celsius) — conditions that should have vaporized the fragile particles.
“It shouldn’t survive,” Veilleux said. “If dust touches gas at 10,000 degrees, it’s going to vaporize it.”
Yet much of the dust endures, likely cocooned by protective cooler gas pockets, according to the statement. Observing these dust grains as they move in and out of galaxies gives astronomers a new window into the life cycle of galaxies and the cosmic recycling of matter.
The researchers propose a survival mechanism called “cloud–wind mixing,” in which dust grains are shielded by cooler pockets of gas while the surrounding hotter gas slowly dissipates. This mechanism explains why PAH emission is detectable at such vast distances from the galaxy, according to the statement.
Follow-up research could aim to push observations even farther, the researchers say, potentially detecting dust in the vast spaces between galaxies. Such a discovery could trace a journey of a million light-years or more, revealing just how far galactic material can travel.
“From the Big Bang to today, galaxies are living beasts in a way,” Veilleux said in the same statement. “They’re still evolving, and that cycle of gas in and out is important in knowing what will happen in the future.”
This research is described in a paper published Aug. 25 in The Astrophysical Journal.
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